Field of the Invention
The present invention relates to a display device, and more particularly, to a display device with an integrated touch screen and a driving method thereof.
Discussion of the Related Art
Touch screens are a type of input device that is included in image display devices such as Liquid Crystal Displays (LCDs), Field Emission Displays (FEDs), Plasma Display Panel (PDPs), Electroluminescent Displays (ELDs), and Electrophoretic Display (EPDs), and allows a user to input predetermined information by applying a pressure (i.e., by pressing or touching) to a touch sensor of a touch screen of the image display device while looking at the image display device.
Particularly, the demand of display devices with an integrated in-cell type touch screen, which include a plurality of built-in elements configuring the touch screen for providing slim portable terminals such as smart phones and tablet Personal Computers (PCs), is recently increasing.
Hereinafter, a related art display device with an integrated touch screen will be described with reference to FIG. 1.
FIG. 1 is a diagram illustrating a configuration of a related art display device with an integrated touch screen, and more specifically illustrates a configuration of a display device with an integrated self-capacitive touch screen having an in-cell type.
The related art display device with the integrated self-capacitive touch screen having an in-cell type, as illustrated in FIG. 1, includes: a panel 10 with a built-in touch screen 11; a display driver IC (DD-IC) 20 that is connected to an external system and controls a plurality of gate lines and data lines in the panel 10; a plurality of touch ICs (T-IC1 and T-IC2) 31 and 32 that drive the touch screen 11 in the panel 10.
The panel 10 includes m number of electrodes 12, and m number of lines 13 that are respectively extended from the m electrodes 12. Each of the touch ICs 31 and 32 includes m number of touch IC channels respectively corresponding to the m lines 13, for self-capacitive touch sensing.
Since one touch IC channel generally corresponds a line connected to an electrode in one-to-one correspondence relationship, as illustrated in FIG. 1, when the number of lines connected to an electrode is more than the number of channels that are capable of being accommodated by one touch IC, a plurality of touch ICs are required to be used, causing the increase in cost.
In the display device with the integrated touch screen of FIG. 1, each of the electrodes 12 is built in the panel 10 and performs a touch function and a display function, and thus is used as a common electrode for display driving when the display device is driven in a display driving mode, or is used as a touch electrode when the display device is driven in a touch driving mode. The display driving mode is a display mode for displaying images on the display device, and the touch driving mode is a touch mode for detecting and processing a touch input to the display device.
On the contrary, when the display device is driven in the display driving mode, a common voltage Vcom outputted from inside the display driver IC (DD-IC) 20 is applied to the electrodes 12 through the touch ICs 31 and 32, in which case the touch ICs 31 and 32 need to accommodate a negative voltage when the common voltage Vcom is the negative voltage.
However, the related art touch ICs 31 and 32 cannot accommodate a negative voltage and thus, a special manufacturing process and design for a touch IC that can accommodate the negative voltage are needed, which in turn increases the manufacturing cost of the touch ICs.
Moreover, when the related art touch sensitive display device is driven in the display driving mode, a ground-level voltage instead of a negative voltage may be incidentally supplied to the electrode 12 through the touch IC, thereby causing the degradation of image quality.
To provide a summary on the above-described limitations, the related art display device with the integrated touch screen has at least the following limitations.
First, as the number of touch IC channels matching the respective lines connected to electrodes increases, the number of touch ICs increases, thereby causing the increase in cost for the display device.
Second, a touch IC is separately manufactured by modifying the manufacturing process and design thereof for applying a negative common voltage, thereby causing the increase in the manufacturing cost of the touch IC.
Third, when the related art touch IC is applied to a display device, the ground-level common voltage, instead of the desired negative common voltage, may be incidentally applied to the electrodes in the display driving mode, thereby causing the degradation of image quality.